Colorectal cancer (CRC) is a significant public health problem. Because treatment of advanced CRC is limited, prospects for CRC control must focus on early detection and prevention. Strong circumstantial evidence suggests that CRC develops from a precursor lesion, the adenomatous polyp. Because the number of individuals with polyps far exceeds the number who develop cancer, advances in CRC control must focus on improving our understanding of the risk factors for developing adenomas and for the transformation of adenomas into colorectal cancers. Obesity, estimated by body mass index, has been consistently linked to CRC risk in men but not in women. Recent epidemiologic data suggest that adipose tissue distribution, and in particular visceral adipose tissue (VAT) rather than overall adiposity, may be an important risk factor for CRC. Dietary fat, meat, and protein intake have also been postulated as risk factors for the CRC but studies have varied. For example, the benefits of polyunsaturated as opposed to saturated fat intake have not been observed in all studies. Previous investigations may have been hampered by using imprecise methodologies to measure obesity or estimate dietary fat intake. Biologic measures are preferable because of their greater precision. I propose to investigate the relationship of visceral adipose tissue and dietary fat intake to adenomatous polyps, the precursor lesion of CRC. Two well established biomarkers with superb reproducibility and successful pilot testing will be employed. Results from these studies will translate rapidly to clinical application and may impact significantly on future prevention efforts.